1. Field of the Invention
The present invention relates to an ink-jet head that ejects ink to a record medium, and also to a connecting structure between a flexible printed circuit and a terminal-formed member.
2. Description of Related Art
Some ink-jet heads include a passage unit, an energy applier, and a flexible printed circuit (FPC). Formed in the passage unit are nozzles that eject ink and pressure chambers that respectively communicate with the nozzles. The energy applier applies ejection energy to ink in the pressure chambers. The FPC supplies a drive signal to the energy applier. Known as the energy applier is, for example, a piezoelectric actuator unit that changes the volume of the pressure chambers and thereby applies pressure as the ejection energy to ink in the pressure chambers (see Japanese Patent Unexamined Publication No. 2002-36568).
The actuator unit disclosed in the aforementioned Publication includes individual electrodes respectively disposed at positions corresponding to the pressure chambers, a common electrode that extends over the pressure chambers, and a piezoelectric sheet sandwiched between the individual electrodes and the common electrode. On the actuator unit, drive-signal terminals electrically connected to the respective individual electrodes and constant-potential-signal terminals electrically connected to the common electrode are disposed. The constant-potential-signal terminals, each of which has a planar area larger than that of the drive-signal terminal, are located on both sides of a group of the drive-signal terminals. On the FPC, drive-signal electrodes and constant-potential-signal electrodes are disposed. Each of the drive-signal electrodes outputs a drive signal generated by a driver IC. The constant-potential-signal electrodes, each of which outputs a constant-potential signal used as a reference against the drive signal, are located on both sides of a group of the drive-signal electrodes. The drive-signal electrodes are respectively bonded to the drive-signal terminals with a solder which is a metal bond, and the constant-potential-signal electrodes are respectively bonded to the constant-potential-signal terminals with a solder. Thereby, the actuator unit and the FPC are connected to each other.
When a drive signal is applied from a drive-signal electrode through a drive-signal terminal to a corresponding individual electrode while the ground voltage as a constant-potential signal is applied from the constant-potential-signal electrode through the constant-potential-signal terminal to the common electrode, a portion of the piezoelectric layer sandwiched between this individual electrode and the common electrode incurs an electric field acting along a thickness direction of the piezoelectric layer, so that this portion of the piezoelectric layer expands. This changes the volume of a corresponding pressure chamber, and pressure as the ejection energy is applied to ink in the pressure chamber.